Trailers used in road trains are typically provided with a relatively simple suspension system. These trailers are typically provided with tandem axles, with each axle being located by means of a trailing or leading arm in conjunction with a Panhard rod or other means for providing lateral location of the axle. Air springs are typically used to provide the load support for the trailer.
While such a suspension arrangement is adequate for most on-road conditions, it would nevertheless be preferable that the trailer be also provided with additional roll support to minimize the roll motion of the trailer. Furthermore, it would be preferable that the wheel assemblies of the trailer be adapted to have relatively free cross-axle articulation motion (also called “warp” motion) where the trailer needs to go over uneven road or off-road surfaces. This will enable the trailer to more safely traverse such uneven surfaces and reduce the loading of a wheel riding up a curb.
The Applicant has developed a number of different hydraulic suspension systems that provide for roll support while at the same time allowing free cross-axle articulation of the wheel assemblies of the vehicles. These suspension systems are for example described in U.S. Pat. Nos. 5,447,332, 5,480,188, 5,562,305, 5,915,701 and 6,010,139. Such systems are however impractical to use on the tandem axles of trailers because of their complexity and cost.
It would however still be advantageous to use a hydraulic or pneumatic suspension arrangement for such tandem axle applications because such an arrangement can be readily retrofitted onto existing suspension systems.
It is therefore an object of the present invention to provide a suspension arrangement which is relatively simple in design, which provides improved roll control while at the same time allowing free cross-axle articulation motion of the wheel assemblies of a vehicle.